Heat resistant money safe door



April 14, 1964 R. F. HOUSTON 3,128,728

HEAT RESISTANT MONEY SAFE DOOR Filed April 6, 1960 2 Sheets-Sheet 1 IN V EN TOR.

Arron/H5.

A ril 14, 1964 Filed April 6, 1960 v R. F. HOUSTON HEAT RESISTANT MONEY SAFE DOOR 2 Sheets-Sheet 2 TOR.

ATTOB/Vfi United States Patent 3,128,728 HEAT RESESTANT MONEY SAFE DGOR Russell F. Houston, Overpeck, @hio, assignor to The Mosler Safe Company, Hamilton, Ohio, a corporation of New York Filed Apr. 6, 1%6, Ser. No. 20,387 2 Claims. ((31. 109-76) This invention relates to safe doors and the method of making same, and more particularly, the invention relates to safe doors constructed of a metal of low thermal conductivity such as steel, the doors having a substantial amount of metal of high thermal conductivity such as copper underlying the outer surface of the door to impart torch resistance to the doors.

Steel safe doors of substantial thickness have been opened, in the past, by unauthorized persons by means of the application of a cutting torch which cuts through the steel. Such a cutting operation is performed by heating a small area of the steel with an acetylene torch or the like until the area reaches a predetermined temperature at which the metal will readily oxidize when subjected to a jet of oxygen. When the metal has attained such temperature, a jet of oxygen is applied to burn a hole in the safe door. The heat of the oxidation or the burning of the steel thereafter maintains the metal at a sufiiciently high temperature for the continuation of the cutting or burning operation.

It has been found that this type of safe cracking can be prevented, or at least made considerably more diflicult by the insertion of copper plates in the door behind the face thereof. The copper underlies almost the entire outer surface of the door. The copper plates, having higher heat conduction than the steel from which the doors are constructed, tend to absorb heat from the localized area of application of the cutting torch and to dissipate that heat rapidly throughout the door mass. The rapid heat dissipation effectively prevents the localized area of the torch from attaining a temperature suflicient to permit its oxidation for cutting purposes.

It has been an objective of the present invention to improve the method of introducing copper into safe doors and to provide an improved safe door having superior heat dissipating characteristics.

The invention will be described in relation to a circular safe door having a central cavity on the inner surface thereof to receive the door locking mechanism. However, it should be understood that the invention is not limited to that particular form of door.

In the past doors of this type have been manufactured by forming an annulus about the periphery of the door and filling the annulus with copper by inserting carefully machined semicircular copper rings into the annulus. This method of fabrication is subject to several disadvantages.

First, it will be appreciated that it is important to provide intimate heat exchange contact between the copper and the steel door. Accordingly, very precise machining is required so that the copper plates will snugly fit in the annulus. Second, however, even the best machining inherently leaves fine grooves on the machined surface and these grooves will prevent full surface-to-surface contact of copper to steel.

The disadvantages of prior practices are avoided by the present invention wherein the copper is introduced into the door by pouring molten copper into the central cavity formed in the door and driving the copper into annular cavities by centrifugal force. By this means the copper is caused to reside in facial contact with the steel much more intimately than is possible by even the most careful and expensive machining operations, whereby the copper 3,128,728 Patented Apr. 14, 1964 much more effectively draws applied heat from the steel of the door to reduce the possibilities of torch penetration.

In the preferred form of the invention, a peripheral annulus is formed in the door and the annulus is connected by a plurality of circumferentially spaced risers to a central cavity. The door is then rotated and the molten copper is poured into the central cavity from which it flows through the risers into the annulus which has been enclosed by a mold cover, the mold cover having been rendered non-adherent to molten copper. Upon solidification of the copper, the mold is removed. When the copper freezes in the annulus and the risers, the columns of copper in the risers secure the copper ring in the annulus. In the preferred form of the invention the central cavity is also wholly or partially filled with copper. Through the connection of the copper in the cavity to the copper in the annulus by the risers, there is formed an integral network of copper underlying substantially the entire outer surface of the door.

Other features and advantages of the invention will appear from the following detailed description of the invention taken in conjunction with the accompanying drawings in which:

FIG. 1 is a cross sectional view of the door formed in accordance with the present invention;

FIG. 2 is a top plan view thereof;

FIG. 3 is a side elevational view partly in section of apparatus through which the method of the invention is provided; and

FIG. 4 is a fragmentary side elevational view of the apparatus taken in the direction of lines 4-4 of FIG. 3.

Each door is formed from a metal blank 10 as shown in FIG. 1, the blank having a central cavity 11 to receive the locking mechanism. The metal from which the blank is formed may be SAE 1020 steel, for example or other hardenable alloy. Bores 12 are formed in the walls of the blank to receive locking bolts, not shown. A central shouldered bore 13 is provided for the passage of a shaft by which the locking mechanism is actuated from the outer surface 14 of the door.

The blank is provided with a peripheral annulus 15 which extends uninterruptedly about the circumference of the door and which extends radially inwardly a distance approximately equal to one-half the radius of the door. A plurality of risers 16 are circumferentially spaced about the door. The risers are angulated radially outwardly from the central cavity 11 to the annulus 15.

As molten copper is introduced into the door, it first completely fills the annulus 15 as indicated at 17, then completely fills the risers as indicated at 18 and then fills all or a portion of the central cavity 11 as indicated at 19 depending on how much is added. The combined copper in the annulus at 1'7 and in the cavity at 19 underlies substantially the entire outer surface of the door. The copper portions 17 and 19 are interconnected by the copper 18 in the risers so as to form an interconnected network of copper. It is preferred that the copper be at least 99.5% pure, for it has been found that the heat conductivity of copper is measurably increased by a decrease in the impurities.

While the preferred form of the invention, the integral network of copper, is utilized, it should be well understood that if desired the copper could be discontinued at the top of the risers and, optionally, a plate of copper 19 positioned into the central cavity.

The method and apparatus for introducing copper into the safe door is best illustrated by reference to FIGS. 3 and 4. The apparatus includes a plate 23 which is rotatably mounted and which is provided with drive means for rotating the plate, the drive means not being shown. The plate has a central opening 24 to receive a plug 25. The plug 25 performs the dual function of positioning the door blank in precise axial alignment with the axis of rotation of plate 23, and plugs the shouldered bore 13 to prevent the flow of molten copper into the bore 13.

Two vertical projecting lugs 26 are secured by means of bolts 27 to the edge of the plate 23. Each lug is provided with a generally horizontal slot 28 which opens in the direction of rotation of the plate 23. Each slot has an upwardly inclined edge 29.

A mold cover 30 is adapted to be positioned on the door blank as shown in FIG. 3. Generally horizontal lugs 31 are secured by bolts 32 to the mold cover, the lugs having end portions 33 which cooperate with the slots 28 in the lugs 26 on the plate 23. As can best be seen by reference to FIG. 4, the mold cover 30 can be clamped on the apparatus and door blank by rotating the mold cover with respect to the plate 23 so as to drive the end portions 33 downwardly along the inclined surface 29. The relationship of the direction of rotation of the apparatus with respect to the slots 28 tends to maintain the mold cover in clamping association with the plate and door blank.

The mold cover has cylindrical side walls 35 and a plate 36 integral with the upper edges of the side walls. The side wall 35 has an annular ring 37 projecting radially inwardly, the ring terminating in a frusto-conical surface which engages a similar surface 38 on the door blank. The location of the engagement of the surface 37 with door blank is above the annulus 15 of the door blank. The lower edge of the cylindrical wall 35 engages the door blank along a circumferential line indicated at 39. The lower portion of the Wall 35, the annular ring 37 and the line contact 39 form a cavity 40 surrounding the annulus 15.

The plate 36 of the mold cover has a central opening 42 through which projects the stem 43 of a cap 44 which is welded as at 45 to the plate 36. The stem has a central bore 46 through which molten copper is poured through a suitable spout 48. The stem is terminated by a circular flange 47 having an outside diameter substantially the same as the inside diameter of the central cavity 11 so that the flange 47 will fit snugly against the walls of the central cavity.

In operation, the plate 23 and the door blank 10 are first heated to a proper temperature, as for example 350- 450 F. By maintaining the door blank at an elevated temperature, the molten copper is prevented from sticking or freezing during the initial pouring into the blank and is permitted to flow freely to the outer extremity of the annulus. The mold cover is heated to a similar temperature. The mold cover, including the cap 44, is blackened with lamp black or the like over the area which will be in contact with molten copper in order to prevent the sticking of the copper to the mold cover. The mold cover is assembled with respect to the door blank 10 and plate 23 and is locked into place by counterclockwise twisting (as viewed from above) to bring the lug end portions 33 into snug engagement with the slots 28. The assembly is rotated at a suitable speed which will be variable depending upon the diameter of the door blank. In one embodiment utilizing an 11 and 11 /2 inch diameter, the assembly is rotated at 700 to 800 rpm. The mold cover is then poured to the cavity 11 through the bore 46 and stem 43. The action of this centrifugal force upon the copper causes the copper to fiow radially outwardly.

The angulation of the risers 16 facilitates the radially outward flow of the molten copper from the cavity 11 through the risers and into the annulus 15. In order to assure complete filling of the annulus 15, the cavity 40 permits the copper to flow beyond the annulus so that a projecting ring of copper will remain after the copper freezes. The thus formed ring will ultimately be machined oil the blank.

The molten copper continues to fill the cavity until it begins to rise upwardly into the stem 43. At this time the pouring of the copper is discontinued. The assembly is continued to be rotated until the copper freezes. After the copper freezes, rotation is discontinued, the mold cover is removed and the blank is taken from the plate 23. The excess copper is machined from the periphral edge and excess copper is machined from the central cavity. A hole aligned with bore 13 is bored in the copper in the central cavity and the blank is ready for further operations necessary to complete the door.

Having described my invention, I claim:

1. A safe door comprising a metallic blank having a circumferential annulus, copper extending without interruption throughout said annulus, said door having a lock receiving central cavity therein and plurality of holes connecting said annulus to said cavity, and a continuum of copper spanning said cavity and filling said holes and being integral with the copper in said annulus.

2. A steel safe door having a groove extending about its periphery, said door having a lock receiving central cavity therein spaced from said groove, and having a plurality of spaced holes connectnig said groove to said cavity, and a continuum of copper spanning said cavity, and filling said holes and said groove.

References Cited in the file of this patent UNITED STATES PATENTS 1,018,606 Casserly Feb. 27, 1912 1,132,902 Bauer Mar. 23, 1915 1,561,845 Goldsmith et al Nov. 17, 1925 1,605,443 Kennedy Nov. 2, 1926 2,274,667 Colwell Mar. 3, 1942 2,391,523 Sorensen Dec. 25, 1945 2,440,952 Hurley May 4, 1948 2,466,277 Rubissow Apr. 5, 1949 2,638,646 Rubissow May 19, 1953 2,731,689 Fannen Jan. 24, 1956 2,770,857 Boissou Nov. 20, 1956 2,833,009 Horst May 6, 1958 2,881,490 Benham Apr. 14, 1959 FOREIGN PATENTS 25,188 Great Britain Nov. 13, 1907 400,274 Great Britain Oct. 23, 1933 

2. A STEEL SAFE DOOR HAVING A GROOVE EXTENDING ABOUT ITS PERIPHERY, SAID DOOR HAVING A LOCK RECEIVING CENTRAL CAVITY THEREIN SPACED FROM SAID GROOVE, AND HAVING A PLURALITY OF SPACED HOLES CONNECTING SAID GROOVE TO SAID CAVITY, AND A CONTINUUM OF COPPER SPANNING SAID CAVITY, AND FILLING SAID HOLES AND SAID GROOVE. 